watchdog.h

// Copyright (c) 2006-2008 The Chromium Authors. All rights reserved.// Use of this source code is governed by a BSD-style license that can be// found in the LICENSE file.// The Watchdog class creates a second thread that can Alarm if a specific// duration of time passes without proper attention. The duration of time is// specified at construction time. The Watchdog may be used many times by// simply calling Arm() (to start timing) and Disarm() (to reset the timer).// The Watchdog is typically used under a debugger, where the stack traces on// other threads can be examined if/when the Watchdog alarms.// Some watchdogs will be enabled or disabled via command line switches. To// facilitate such code, an "enabled" argument for the constuctor can be used// to permanently disable the watchdog. Disabled watchdogs don't even spawn// a second thread, and their methods call (Arm() and Disarm()) return very// quickly.#ifndef BASE_WATCHDOG_H__#define BASE_WATCHDOG_H__#include <string>#include "base/condition_variable.h"#include "base/lock.h"#include "base/logging.h"#include "base/platform_thread.h"#include "base/time.h"class Watchdog {
public:
// Constructor specifies how long the Watchdog will wait before alarming.
Watchdog(const base::TimeDelta& duration,
const std::string& thread_watched_name,
bool enabled);
virtual ~Watchdog();
// Start timing, and alarm when time expires (unless we're disarm()ed.)void Arm(); // Arm starting now.void ArmSomeTimeDeltaAgo(const base::TimeDelta& time_delta);
void ArmAtStartTime(const base::TimeTicks start_time);
// Reset time, and do not set off the alarm.void Disarm();
// Alarm is called if the time expires after an Arm() without someone calling// Disarm(). This method can be overridden to create testable classes.virtualvoid Alarm() {
DLOG(INFO) << "Watchdog alarmed for " << thread_watched_name_;
}
// Reset static data to initial state. Useful for tests, to ensure// they are independent.staticvoid ResetStaticData();
private:
class ThreadDelegate : public PlatformThread::Delegate {
public:
explicit ThreadDelegate(Watchdog* watchdog) : watchdog_(watchdog) {
}
virtualvoid ThreadMain();
private:
Watchdog* watchdog_;
void SetThreadName() const;
};
enum State {ARMED, DISARMED, SHUTDOWN };
bool init_successful_;
Lock lock_; // Mutex for state_.
ConditionVariable condition_variable_;
State state_;
const base::TimeDelta duration_; // How long after start_time_ do we alarm?const std::string thread_watched_name_;
PlatformThreadHandle handle_;
ThreadDelegate delegate_; // Store it, because it must outlive the thread.
base::TimeTicks start_time_; // Start of epoch, and alarm after duration_.// When the debugger breaks (when we alarm), all the other alarms that are// armed will expire (also alarm). To diminish this effect, we track any// delay due to debugger breaks, and we *try* to adjust the effective start// time of other alarms to step past the debugging break.// Without this safety net, any alarm will typically trigger a host of follow// on alarms from callers that specify old times.static Lock static_lock_; // Lock for access of static data...// When did we last alarm and get stuck (for a while) in a debugger?static base::TimeTicks last_debugged_alarm_time_;
// How long did we sit on a break in the debugger?static base::TimeDelta last_debugged_alarm_delay_;
DISALLOW_COPY_AND_ASSIGN(Watchdog);
};
#endif // BASE_WATCHDOG_H__